title: Disruption of downstream MyD88 or TRIF Toll-like receptor signaling does not protect against cerebral ischemia.
abstract: Toll-like receptor (TLR) signaling plays an important role in cerebral ischemia, but downstream signaling events, which can be organ-specific, are incompletely understood. We thereby investigated involvement of the MyD88-dependent (MyD88) and MyD88-independent (TRIF) TLR signaling pathways in 2 in vitro and 2 in vivo models of cerebral ischemia. For in vitro studies, we used a model of oxygen-glucose deprivation (OGD) followed by flow cytometric analysis to determine:1) viability of PC12 cells following knock-down with MyD88 siRNA compared to negative control siRNA and 2) viability, apoptosis and necrosis of cortical neurons from MyD88 null (-/-) , TRIF mutant, and wild type (WT) mice. In addition, in vivo, 1) We examined CA1 neuronal survival 7 days after global forebrain ischemia and 2) infarct volumes 24h after Middle Cerebral Artery Occlusion (MCAO) in all 3 types of mice. OGD: 1) There were no differences in either percent viability of PC12 cells transfected with MyD88 compared to negative control siRNA or 2) in percent viability, apoptosis and necrosis of cortical neurons from MyD88-/-,TRIF mutant and WT mice. Global ischemia: neuronal survival was similar in all 3 groups of mice. Finally, MCAO: infarct volumes were not statistically different among all 3 groups of mice: MyD88-/-, 23.9±9.9 mm(3), TRIF mutant, 26.7±5.8 mm(3) and WT, 17.9±8.4mm(3). These findings show that disruption of MyD88 or TRIF signaling does not confer protection in brain ischemia and suggests the possibility of additional or alternate downstream adaptors during TLR signaling in cerebral ischemia.
authors.affiliation: Stroke Branch, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Building 10, Rm 5B06, MSC 1401, Bethesda, MD 20892-1401, USA. famakinb@ninds.nih.gov
authors.forename: Bolanle M
authors.initials: BM
authors.lastname: Famakin
authors.forename: Yongshan
authors.initials: Y
authors.lastname: Mou
authors.forename: Christl A
authors.initials: CA
authors.lastname: Ruetzler
authors.forename: Joliet
authors.initials: J
authors.lastname: Bembry
authors.forename: Dragan
authors.initials: D
authors.lastname: Maric
authors.forename: John M
authors.initials: JM
authors.lastname: Hallenbeck
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D002545:Brain Ischemia / Q000378:metabolism*; D002469:Cell Separation; D005434:Flow Cytometry; D055785:Gene Knockdown Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D009336:Necrosis / Q000378:metabolism; D016716:PC12 Cells; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D053594:Myeloid Differentiation Factor 88; D034741:RNA, Small Interfering; C507780:Myd88 protein, mouse; C507781:Myd88 protein, rat; C476286:Ticam1 protein, mouse